The present invention relates generally to apparatus and methods for forming individual foam-filled bags commonly used as protective cushions in the packaging arts. More particularly, the present invention relates to an improved device and an apparatus for forming such protective cushions by dispensing two streams of reactive foam components between opposing panels of a flexible sheet material and diverting, or deflecting, one of the two reactive foam component streams into the path of the other of the two streams to more fully promote mixing of the reactive foam components together therebetween in order to produce an expandable foam between the panels.
In the packaging industry, expandable foams have been used for some time to form protection for packaged articles. Conventional practice in such industry has included filling a cardboard box with an expandable foam, such as a urethane or polyurethane foam, and contacting the foam with a plastic barrier sheet to create a protective cushion and then placing an article for shipping into the box on the cushion. The article may then also be covered with another plastic sheet and a second filling of expandable foam accomplished before closing the box.
Another practice in the industry utilizes foam cushions which are inserted into the packing box immediately after the foam cushions are made. This is accomplished by machines which react two foam components together within a gun apparatus and then dispense the foam so formed between two opposing plastic sheets, and then seal the edges to form a protective foam cushion. Numerous patents exist which describe such methods and apparatus. Two such patents, U.S. Pat. No. 4,999,975, issued Mar. 19, 1991 and U.S. Pat. No. 4,800,708, issued Jan. 31, 1989 describe apparatus for foam cushion making in which a foam dispenser, or gun, is positioned between two opposing plastic panels. Two different reactive foam components, commonly referred to as foams precursors, are mixed together in the foam gun in order to form the foam, which is then dispensed under pressure between the two opposing plastic panels to form the foam protective cushions.
Although such apparatus and methods are operational and produce protective foam cushions which adequately provide protection to packaged articles, they are not without certain inherent disadvantages. For example, they reply upon a mixing chamber or cartridge in the foam gun to provide an area where the two foam components are mixed together to form the expandable foam. Once formed, the foam is then dispensed under pressure through a nozzle downstream of the mixing chamber. The mixing chamber typically accumulates bits of hardened foam over time and thus must be cleaned at regular intervals, typically at weekly intervals often by flushing the system with a solvent. At this time, the apparatus may have to be taken apart to be cleaned, thereby leading to detrimental downtime of the apparatus.
Other apparatus rely upon a complex foam dispensing gun structure which utilizes two ports to convey the two reactive foam components to a mixing chamber preceding the dispensing end of the gun. In this type apparatus, the mixing chamber may include a valving rod which slides in and out of the mixing chamber to control the flow of at least one of the reactive foam components. This type of apparatus is also not without certain disadvantages, for although the valving rod effectively acts as a valve to control the flow of the reactive foam components into the mixing chamber, the foam formed by the reactive components has been known to slowly build up in the mixing chamber and on the valving rod itself. Additionally, when a valving rod is used, "crossover" between the foam components may occur when one of the foam components accumulates on the valving rod and makes contact with into the other foam component as the valving rod slides back and forth to form a reacted, hardened foam. The valving rod then must be cleaned, which typically requires scraping the accumulated foam off of the valving rod or flushing the system with a solvent. Each cleaning wears down the tolerance of the rod to eventually wear down the overall effectiveness of the foam dispensing gun of these devices.
In order to prevent the buildup of reacted foam in the mixing chamber and dispensing nozzles of the aforementioned apparatus, solvent systems have been developed that continuously dispense solvents through the foam dispensing systems used therein in order to maintain them in a clean state. These solvent systems increase the complexity and cost of the apparatus and often, the solvent(s) used may have a detrimental effect on the dispensing apparatus over long-term use or on the bags into which the foam is dispensed.
U.S. Pat. No. 5,727,370 issued Mar. 17, 1998 and assigned to the assignee of the present invention describes an apparatus for producing foam cushions wherein two separate streams of reactive foam components are dispensed through separate nozzles into a flexible mixing chamber that is formed by two opposing panels of a plastic web that forms the exterior surface of the final foam cushion. In this apparatus, a solvent-free system is provided by directing the two streams of reactive foam components to an area between two opposing walls of a continuous plastic bag. Two separate tubes convey and direct the foam components at each other. Although effective, this apparatus utilizes ordinary nozzles on the ends of its dispensing tubes and it has been discovered that one of the two foam components does not always fully mix with the other of the two foam components.
The present invention is directed to an apparatus and methods for producing foam cushions which overcomes these disadvantages and which promotes more efficient mixing of the two reactive components.